Estimating corrosion attack in reinforced concrete by means of crack opening

Degradation of reinforced concrete (RC) structures is a serious safety problem affecting all industrialized countries, and the economical aspect of this problem cannot be neglected. One of the main reasons for the degradation of RC is the corrosion of steel reinforcing bars as a result of concrete cover cracking and reduction in bar cross section. As a consequence, the structural capacity of RC elements decreases progressively as degradation develops. Nondestructive testing and/or analytical formulation represent high-quality rapid methods for evaluating the corrosion penetration of bars and provide useful parameters for designing retrofits. This paper presents an additional tool that can be used to evaluate and assess the vulnerability of existing structures in terms of the determination of bar cross section lost. Using simple charts and formulas, this can be accomplished by calculating reinforcing bar cross section loss due to corrosion by measuring external crack widths in the concrete cover. Predictions were obtained by using two analytical models developed. These predictions have been satisfactorily compared with both the literature and new experimental results, as well as with previous empirical models available in the scientific literature. The experimental results were obtained by corroding real-scale concrete specimens reinforced with smooth and ribbed bars (according to old and modern building codes) using 3.5 wt% sodium chloride solution and an applied current

Section: Experimental Testssupporting

confidence: 88%

Section: State Of the Artmentioning

confidence: 99%

Section: State Of the Artmentioning

confidence: 99%

w_{c} = 15.863 \cdot {(\frac{x_{aver}}{R_{0}} \cdot C T)}^{0.928}

where w c is in millimeters.…”

Section: State Of the Artmentioning

confidence: 99%

See 2 more Smart Citations

Nondestructive assessment of corrosion of reinforcing bars through surface concrete cracks

Bossio

Lignola

Fabbrocino

et al. 2017

“…There is agreement on the fact that the thickness and the porosity of the concrete cover are the most important factors for the durability of reinforced concrete. In particular, to correlate the crack width and the corrosion, two fundamental parameters have to be taken into account: the ratio of the concrete cover to the rebar diameter and the concrete strength. A distinction between ordinary concrete and high strength concrete (HSC) should be considered.…”

Section: Introductionmentioning

confidence: 99%

A review of literature and code formulations for cracking in R/C members

Lapi

Orlando

Spinelli

2018

Cracking in R/C members is a complex phenomenon characterized by high scattering, mainly affected by concrete in tensile zone. The aim of this paper is to evaluate the effectiveness of formulas for crack width prediction developed in last decades. First, an historical review of available literature models is presented and discussed. Second, the progress and missteps, which have characterized the development of international code provisions, are shown. Finally, a comprehensive comparison between predicted crack widths and experimental data is performed. Some formulas more than others provide mean values of crack width in good agreement with experimental data; nevertheless, predictions are always very scattered, as ratios between theoretical and experimental values have a coefficient of variation not lower than 30%. Results show that the prediction capacity does not necessarily increase as the cracking model is refined.

Corrosion of anchorage head system of post‐tensioned prestressed concrete structures under chloride environment

Luo

Liu

2017

Corrosion of anchorage head system may lead to severe structural failure. To understand the characteristics of corrosion and the risks of anchoring failure, 11 posttensioned prestressed concrete specimens with single-hole anchorage-plate system sealed with postcast concrete contaminated by NaCl were fabricated and then corroded for 8 months. By periodically monitoring corrosion current density and breaking the specimens to detect mass loss, the time-varying law of corrosion rate and the influences of chloride concentration and cover layer depth on corrosion rate were found. The mean corrosion rate of each component of anchorage head system varies with effective prestress level in a light growing trend with approximate linear relationship. The plates were corroded most severely and manifested relatively full and uniform corrosion characteristics, whereas the barrels and wedges were corroded slightly and exhibited relatively local and pitting corrosion characteristics. The average corrosion rate of the plates is 50 times and 80 times higher than that of the barrels and wedges, respectively. The interfaces of the contacted components were hardly corroded. Finally, the corrosion risk of the anchorage head system was analyzed. K E Y W O R D S anchorage head system, chloride environment, corrosion, post-tensioned prestressed concrete structures 1 | INTRODUCTIONPost-tensioned (PT) prestressed concrete (PC) structures have been extensively applied in constructing physical infrastructure. Some structures are in corrosive environments, such as marine, salt lake, salinized grounds, and deicing salt environments where the prestressing system (i.e., the prestressing steel bars, corrugated tubes, and anchorage and coupler system) corrode easily. 1 Even though in a normal atmospheric environment, corrosion can occur due to the carbonization process taking place within the concrete. Compared with ordinary steel bars, the prestressing system has more strength and less ductility and cross sectional area; thus, corrosion may induce severe structural failure. According to surveys, 2-4 a series of accidents happened worldwide in the last decades because of the corrosion failure of PT PC structures.The main cause for the majority of the accidents involving corrosion failure is the prestressing steel bar corrosion. However, the corrosion of anchorage and coupler system is also a non-negligible cause of corrosion failure. Because the transverse outlines of anchorage and coupler systems are larger than that of prestressing tendons, which means that the cover layers of the former are less than that of the latter, the anchorage and coupler systems would be corroded prior to the prestressing tendons. In some unbonded systems, the prestressing tendons are protected with polyethylene cannulas while the anchorage head systems are protected only with cover concrete, thus the corrosion risk of the anchorage head systems is much more than that of the prestressing tendons. In fact, there were some literatures which had documented the corrosion acc...